This invention relates in general to vehicle wheels and in particular to a light weight wheel which has a layer of sealant disposed upon a portion of a surface of the wheel to assure that the wheel is air tight.
Light weight vehicle wheels formed from an alloy of a light weight metal such as aluminum, magnesium or titanium, are replacing steel wheels on an increasing number of vehicles. Such light weight wheels provide both a reduction in weight from steel wheels and an attractive appearance. Referring now to the drawings, there is shown in FIG. 1 a fragmentary sectional view of a typical prior art one piece light weight wheel 10.
The wheel 10 has an annular wheel rim 11 which is adapted to carry a vehicle tire. The outboard end of the wheel rim 11 includes an annular sidewall 12. Due to limitations of conventional casting processes, the sidewall 12 typically has a thick cross section. An outboard tire bead retaining flange 13, which extends in an outward radial direction, is formed upon the outboard end of the sidewall 12. An annular outboard tire bead seat 14 is formed in the outer surface of the sidewall 12 adjacent to the outboard tire bead retaining flange 13. The outboard tire bead seat 14 extends axially from the outboard flange 13 to an annular outboard tire bead hump 15. The outboard tire bead hump 15 is connected by a radial deep well wall 16 to a recessed annular deep well 17. The deep well 17 extends axially to an annular leg portion 18 of the wheel rim 11. The inboard end of the leg portion 11 is formed as an annular inboard tire bead hump 19. The inboard tire bead hump 19 is adjacent to an inboard tire bead seat 20 which extends axially from the inboard tire bead hump 19 to an inboard tire bead retaining flange 21. The inboard tire bead retaining flange 21 extends in an outward radial from the inboard end of the wheel rim 11.
The wheel 10 also has a wheel disc 25 which is formed across the outboard end of the wheel rim 11. The wheel disc 25 includes a wheel hub 26 having a central pilot hole 27 and a plurality of wheel lug holes 28 (one shown) formed therethrough. A plurality of spokes 29 (one shown) extend radially from the hub 26 to the wheel rim sidewall 12 and support the wheel hub 26 within the wheel rim 11.
A flow chart for a typical prior art process for forming the wheel 10 is shown in FIG. 2. In functional block 30, a one piece vehicle wheel casting is formed by a conventional casting process, such as gravity or low pressure casting. The wheel casting is machined to final shape in functional block 31. Typical machining operations include turning the tire bead seats, facing the inboard surface of the wheel hub, boring the pilot hole and drilling the wheel lug holes.
Once the machining is completed, the wheel surface is cleaned in preparation for finishing, as shown in functional block 32. Preparation usually includes immersion in a mild acid bath to remove all machining lubricants and rinsing with water sprays to remove the acid. Additionally, the surface of the wheel may be polished to a high luster, as shown in functional block 33; however, this step is optional. Depending upon the process used, the polishing step may require additional surface preparation to clean polishing residue from the wheel surface. In functional block 34, the wheel is dried by heating to approximately 250.degree. F. in a drying oven. The heating evaporates any rinse water which may have been retained in small pores formed in the surface of the wheel. If not removed from the surface pores, such water could be changed to steam during the curing of a coating applied to the wheel surface in the next step of the process. The expansion of the steam could rupture the coating, thereby marring the appearance of the finished wheel.
In functional block 35, a coating is applied to the wheel. For a polished light weight wheel, the coating is usually a clear coat which protects the polished surface. The clear coat can be applied to the entire wheel or only to the outboard surface of the wheel disc 25. Alternately, a decorative coat of paint can be applied to all or a portion of the outboard surface of the wheel disc. The coating is cured in functional block 36 by heating the wheel in a curing oven to about 350.degree. F. A second clear coat (not shown) is usually applied over the coat of paint and cured to protect the painted surface.